Morphological anomalies in the placentae of IVF pregnancies: preliminary report of a multicentric study.

Macroscopic characteristics of 100 fetal adnexae from pregnancies obtained by in-vitro fertilization and embryo transfer (IVF-ET) were compared with data for normal pregnancies taken from the literature. Material was obtained from 63 singleton, 15 twin, one triplet and one quadruplet pregnancies. The fetal and placental weights as well as the fetal:placental weight ratio were within the normal range for gestational age. Whilst placental morphology was normal, the insertion of the umbilical cord was frequently abnormal. Marginal (15%) and velamentous (14%) insertions of the umbilical cord were found more frequently than in a general obstetrical population (6% and 1% respectively). Excluding placentae from multiple pregnancies (which are known to have a higher incidence of abnormal cord insertion) the frequency did not decrease and remained significantly higher than in a normal population (P less than 0.01 and P less than 0.001, for marginal and velamentous insertion respectively). Abnormal insertion of the cord is of major clinical importance because of its association with vasa praevia and fetal haemorrhage (Benkiser Syndrome). Since this condition is thought to be caused by disturbed orientation of the blastocyst at implantation it is probably related to the IVF-ET procedure.